DESCRIPTION (Applicant's Description) The incidence of malignant melanoma of the skin is increasing faster than any other cancer in the United States. Sun exposure is the major etiologic risk factor implicated in the development of melanoma. As the number of estimated new cases and deaths from melanoma continue to rise, discerning the most important timing of sun exposure and the magnitude of the effect is important. While not uncovering new hypotheses, meta-analyses conducted on previous studies evaluating associations between potential risk factors and melanoma may help to guide the search for the etiologies of this disease in future case-control studies and prevention efforts. For this, we need to have a better understanding of the current information on sun exposure and possible confounding effects of the skin's sensitivity to the sun. The various techniques suggested by researchers for meta-analysis can be generally summarized into two approaches: combination of significance levels and combination of effect sizes. In this study, we plan to look at a variation on combining effect sizes by combining relative risk estimates. Relative risk estimates will be pooled using a weighted least square method assuming a fixed effects model, a random effects model (when studies are heterogeneous) and a linear dose-response model. The overall aims of this proposal are to conduct research relevant to melanoma etiology by combining relative risk estimates (RRs) and their variances from previously conducted studies to examine both the strengths and consistency of the observed associations. The relationship between melanoma and 1) timing of sunburns, 2) sunscreen use, 3) tanning salon use, and 4) cumulative sun exposure will each be examined separately by combining risk estimates from each study for an overall relative risk estimate along with combined estimates by study design (e.g., cohort, case-control, hospital controls, and population-based controls), and by method of data abstraction. Studies will also be examined by whether or not they are adjusted for sun-sensitivity (light complexion, tendency to burn, inability to tan, etc.). When data is available, we will also examine the possible effect modification of the relation between melanoma and 1) timing of sunburns, 2) sunscreen use, 3) tanning salon use, and 4) cumulative sun exposure by sun-sensitivity in an attempt to better understand this important interaction. This potential interaction may explain some of the conflicting results in the literature.